Alkoxysilanes are useful as a variety of silane coupling agents and raw materials for insulating thin films and heat resistant materials. In particular, in view of the matter that vinyl trialkoxysilanes can be derived into a variety of polymer materials, a demand thereof is high, and processes of producing the same inexpensively and efficiently are being required.
As the industrial production process of alkoxysilanes, the following processes using a chlorosilane as the intermediate raw material are known.
(1) Production Process of Alkoxysilanes Having an Unsaturated Bond:
For example, vinyl trialkoxysilanes are produced by hyrosilylating trichlorosilane and acetylene in the presence of a platinum catalyst to obtain vinyl trichlorosilane as an intermediate raw material and reacting it with an alcohol (for example, see J. Am. Chem. Soc., 68, 2282 (1964)).
This production process is similarly applicable to the production of vinylalkyl dialkoxysilanes or vinyldialkyl alkoxysilanes.
(2) Production Process of Alkoxysilanes Not Having an Unsaturated Bond:
For example, alkyl trialkoxysilanes are produced by reacting an alkyl trichlorosilane with an alcohol.
This production process is similarly applicable to the production of dialkyl dialkoxysilanes, except for using a dialkyl dichlorosilane as the raw material (for example, see German Patent No. 2,800,017 and European Patent No. 107,765).
However, the above production process using the chlorosilane as the (intermediate) raw material involves the following problems.
Large amounts of hydrochloric acid and chlorine-containg compounds are formed as by-products.
For that reason, a purification step of alkoxysilanes is necessary, and complicated operations such as distillation are required.
Further, since hydrochloric acid formed as a by-product corrodes reactors, corrosion-resistant and expensive reactors are required.
As the industrial production process of alkoxysilanes not using a chlorosilane as the intermediate raw material, the following processes by hydrosilylation are known.
(3) Production Process of Alkoxysilanes Having an Unsaturated Bond:
An organosilicon compound having an H—Si bond is reacted with an alkyne compound such as acetylene. As the foregoing organosilicon compound, trialkoxysilanes, alkyl dialkoxysilanes, or dialkyl alkoxysilanes can be used as the raw material.
(4) Production Process of Alkoxysilanes Not Having an Unsaturated Bond:
An organosilicon compound having an H—Si bond is reacted with an olefin compound such as ethylene. As the organosilicon compound, the same compounds as in (3) can be used as the raw material.
However, according to the conventional production processes (3) and (4), the hydrosilylation is carried out in a solvent, and there are encountered the following problems.
A large amount of the solvent as deteriorated due to recycle use must be subjected to incineration.
For that reason, the product cost increases.
Further, carbon dioxide is generated by the incineration, thereby injuring the environment.
As the production process of alkoxysilanes using neither a chlorosilane as the intermediate raw material nor a large amount of a solvent, a method of subjecting an organosilicon compound having an H—Si group and acetylene to hydrosilylation in vapor phase in a loop reactor equipped with a jet nozzle is known (see JP-A-10-59982).
However, even in this method, a small amount of a solvent for forming a jet is necessary, and a special reactor is necessary. Accordingly, further improvement is still required as the inexpensive and efficient production process of alkoxysilanes while taking into consideration the environmental problem.
As the process of producing organosilicon compounds inexpensively and efficiently while prolonging the life of a catalyst, a method is known in which trichlorosilane and acetylene are subjected to hydrosilylation in vapor phase in the presence of a polyethylene glycol solution of hexachloroplatinic(IV) acid supported on a silica gel, thereby obtaining vinyl trichlorosilane in high yield (see 86th Catalysis Society Meeting (Part A), Preprint, 4H23, page 365 (September 2000), Tottori).
On review of the subject technology, effectiveness of a variety of catalysts was evaluated, thereby obtaining the following conclusion.
When H2PtCl6 was dissolved in polyethylene glycol, a lowering of activity even after elapse of 6 hours after start of the reaction was not observed, and the life of a catalyst was prolonged.
The technology presented at the above Catalysis Society Meeting is concerned with hydrosilylation between trichlorosilane and acetylene. However, in the case that an organosilicon compound having a hydrogen-silicon bond but not containing chlorine is used as the raw material, this technology is unclear on whether or not the same high catalytic activity is obtained.
Rather, it may be considered that since the reaction rate of hydrosilylation between a chlorosilane and an organic compound having a carbon—carbon unsaturated bond, the reaction in vapor phase is easy. However, since an organosilicon compound having a hydrogen-silicon bond but not containing a halogen group is low in reactivity, it is generally considered that the efficiency of hydrosilylation in vapor phase is poor.
In the present circumstances, any review is not made on hydrosilylation in vapor phase using an organosilicon compound having a hydrogen-silicone bond but not containing a halogen group as the raw material.
An object of the present invention is to provide a process of producing alkoxysilanes, which does not use a chlorosilane as the intermediate raw material, is improved in view of the environment, and is satisfactory with respect to the yield of a desired material.